JMIR PEDIATRICS AND PARENTING

Matsumoto et al

Original Paper

Effectiveness of Unguided Internet-Based Cognitive Behavioral
Therapy for Subthreshold Social Anxiety Disorder in Adolescentsand Young Adults: Multicenter Randomized Controlled Trial
Kazuki Matsumoto1, PhD; Sayo Hamatani2,3, PhD; Kiko Shiga4, PhD; Kiyoko Iiboshi4, PhD; Makiko Kasai5, PhD;
Yasuhiro Kimura6, MA; Satoshi Yokota7, MA; Katsunori Watanabe8, PhD; Yoko Kubo9, MA; Masayuki Nakamura10,
MD, PhD
1

Division of Clinical Psychology, Kagoshima University Hospital, Research and Education Assembly Medical and Dental Sciences Area, Kagoshima
University, Kagoshima, Japan
2

Research Center for Child Mental Development, University of Fukui, Fukui, Japan3

Department of Child and Adolescent Psychological Medicine, University of Fukui Hospital, Fukui, Japan

4

Department of Clinical Psychology, Faculty of Human Relations, Shigakukan University, Kagoshima, Japan

5

Clinical Psychology Course, Naruto University of Education, Tokushima, Japan

6

Department of Welfare Psychology, Faculty of Welfare, Fukushima College, Fukushima, Japan

7

Kochi Kokusai High School, Kochi, Japan

8

Department of Psychology, Jin-ai University, Fukui, Japan

9

Graduate School of Clinical Psychology, Kagoshima University, Kagoshima, Japan10

Department of Psychiatry, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan

Corresponding Author:
Kazuki Matsumoto, PhD
Division of Clinical Psychology, Kagoshima University Hospital
Research and Education Assembly Medical and Dental Sciences Area
Kagoshima University
1-8-35 Sakuragaoka
Kagoshima, 8908520
Japan
Phone: 81 0992655707
Email: k2782199@kadai.jp

Abstract
Background: Social anxiety disorder (SAD) is a common mental disorder in adolescents and young adults. Early intervention
and support could help prevent the development of full-blown SAD. Considering that adolescents with social anxiety symptoms
do not prefer face-to-face sessions due to their fear of communicating with therapists, internet-based cognitive behavioral therapy(ICBT) was implemented.
Objective: This study aimed to examine the effectiveness of complete self-help ICBT for subthreshold SAD in high school andcollege students with no history of mental disorders.
Methods: A multicenter randomized controlled trial designed to demonstrate the objective was conducted from December 2022
to October 2023. Participants were students enrolled at 6 universities and 1 high school. The intervention was a complete self-help
ICBT and consisted of 10 text-based sessions that taught cognitive behavioral therapy techniques for social anxiety in youths andyoung adults. The comparison was a no-treatment condition (control group), which was randomly assigned in a 1:1 ratio by acomputer program. A total of 2 psychological scales were used to assess the severity of social anxiety, and 1 psychological scaleeach was used to measure symptoms of depression, general anxiety, and quality of life.
Results: In total, 77 students were enrolled as study participants. Through the randomization procedure, 38 participants were
included in the intervention group, and 39 patients were included in the control group. Results from the analysis of covariancewith depression as covariates showed that the participants in the intervention group had significantly reduced symptoms of social
anxiety, depression, and general anxiety compared to the control group. The response rate was 61% (19/31) in the intervention
group and 24% (9/38) in the control group: odds ratio (OR) 4.97 (95% CI 1.61-16.53; P=.003) in the Fisher exact test. The
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recovery rate was 68% (21/31) in the intervention group and 34% (13/38) in the control group: OR 3.95 (95% CI 1.32-12.56;
P=.008). The OR for the remission ratio was 2.01 (95% CI 0.64-6.60; P=.20) and for the risk of worsening was 0.23 (95% CI
0.002-1.33; P=.10), but no significant difference was observed.
Conclusions: The results of this randomized controlled trial show that fully unguided ICBT improves subthreshold SAD inadolescents and young adults. Interpretation of the effectiveness in preventing SAD that meets the diagnostic criteria is limited
by sample size and the follow-up period. Future studies should include more extended observations and larger sample sizes inhigh-risk populations.
Trial Registration: UMIN-CTR UMIN000050064; https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000057035(JMIR Pediatr Parent 2024;7:e55786) doi: 10.2196/55786
KEYWORDS
adolescent; social anxiety disorder; general anxiety; adolescents; teens; social anxiety; teenagers; internet-based cognitive
behavioral therapy; self-help; randomized controlled trials; young adults; cognitive behavioral therapy; anxiety; mental health;students; colleges; universities; social socialize; anxious; fear; mobile phone

Introduction
Background
Social anxiety disorder (SAD) is a mental disorder characterized
by excessive anxiety and embarrassment in social situations
and fear of being negatively evaluated [1]. The lifetime
prevalence of SAD is 4% [2], with a prevalence of 2.1% in
adolescents and young adults [3]. Anxiety disorders, including
SAD, are the most common psychiatric disorders [4], and mild
(subthreshold) forms are common and cause significant
disability [5]. The onset of SAD often occurs in the early to
midadolescent years [6], with most of the patients having thedisorder before their 20s [7]. The adolescent years represent alife stage where interpersonal relationships become more
complex, leading to a heightened susceptibility to anxiety insocial situations. Quite a few young individuals, even those who
do not meet the diagnostic criteria, are aware of experiencing
social anxiety at levels below the threshold for diagnosis. For
example, a previous study reported 280 high school students inJapan found that approximately 20% experienced moderatesocial anxiety over a period of 3 years [8]. Another research
focused on social fears and SAD among Portuguese youth, and
26% reported with intense self-reported social fear [9]. The
presence of subthreshold anxiety disorders increases the risk offull-blown anxiety disorders by more than 3-fold [10]. Treating
subthreshold anxiety disorders in a timely manner may preventthe onset of full-blown anxiety disorders [11]. When adolescentsdevelop SAD, it can negatively affect their interpersonal
relationships, academic achievement, and career development[12]. Intervention for subthreshold SAD is crucial, as it holds
the potential to prevent these issues from arising in the firstplace.

Cognitive Behavioral Therapy for SAD
Cognitive behavioral therapy (CBT) is one of the most effective
treatment approaches for SAD [13]. By modifying the cognitive
behavioral cycle that sustains social anxiety [14], a strong
therapeutic effect can be achieved [15]. The effectiveness offace-to-face individual CBT has been established not only for
adults but also for children and adolescents [16]. However, lowrates of in-person CBT and poor access make it challenging toprovide long-term treatment [17]. The low prevalence of CBT
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behavioral therapists and its high costs in terms of time andfinances [18]. Barriers to mental health treatment have been
identified via interviews of patients with SAD. These barriers
include a lack of awareness of available treatment facilities,
fear of self-disclosure, and financial constraints due to a lackof insurance coverage [19]. Additionally, approximately 80%
of adults with SAD developed the condition during adolescence[20]. Adolescence is a period of establishing autonomy, and as
the scope of social responsibilities expands, young people tend
to hesitate to seek support from others [21]. Access toappropriate treatment remains limited, as many youth do notseek help [22]; this problem is further exacerbated by theshortage of mental health services available worldwide [23]. In
resource-limited situations, therapeutic approaches must be
refined to improve access to treatment. An early intervention
to address the mental health needs of youth could lead to rapid
recovery or prevent relapse of mental health problems [24].

Internet-Based CBT for SAD
Internet-based CBT (ICBT) is a promising solution that canovercome physical barriers and time constraints. Many ICBT
programs have been implemented, and recently, countries withhigh smartphone penetration and internet use have begun tovalidate the effectiveness of self-help ICBT [25,26]. Self-help
programs usually have high dropout rates, but the feature of nothaving to interact with the therapist has been reported to help
reduce the dropout rate of patients with SAD and lead tosatisfactory treatment completion rates [27,28]. A previous
study including individuals with nonclinical anxiety disorders
has also confirmed a significant reduction in anxiety symptoms
through complete self-help ICBT: 50 cases underwent a
web-based ICBT for SAD [29]. Furthermore, conducting ICBT
through mobile devices such as smartphones or tablet PCs, as
opposed to desktop computers, may enhance therapeutic effects.
Social situations eliciting social anxiety are often present outside
the home or private spaces, and intervention through mobile
devices facilitates the immediate recall and implementation of
CBT techniques when confronted with these situations.
Unguided ICBT for individuals with SAD using mobile devices
has demonstrated a high effect size with a range of Cohen
d=0.81 when compared to a waitlist group using the Leibowitz
Social Anxiety Scale (LSAS) total score [28,30].
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JMIR PEDIATRICS AND PARENTINGICBT for Subthreshold SAD
However, there is currently no study examining the effectivenessof unguided ICBT for subthreshold SAD treatment providers.
Due to not meeting the diagnostic criteria, individuals withsubthreshold SAD may have lower motivation and potentiallyhigher dropout rates in self-help treatment. Moreover,adolescents with mild to moderate symptoms of social anxiety
may show a small or limited treatment response. On thecontrary, subthreshold SAD may exhibit a higher averagetreatment response rate, potentially surpassing the 53.6%
observed in diagnosed SAD [31], as it lacks the functional
impairments such as depression and avoidance frequently
observed in patients with SAD [32]. Due to these remaining
areas of uncertainty, it is inappropriate to simply extrapolate
evidence from diagnosed SAD when considering theapplicability of unguided ICBT to subthreshold SAD.

Objective
The aim of this study was to assess the effectiveness ofintervening in widespread subthreshold SAD during adolescenceand evaluate the acceptance of unguided, completely self-help
ICBT, taking into consideration dropout.

Methods
Ethical Considerations
The research protocol underwent review and was approved by
the ethics review board of the Clinical Research Management
Center at Kagoshima University Hospital (ID 220196).
Participants received both oral and written explanations of thestudy and were enrolled upon expressing their voluntary writtenconsent. For high school participants, written consent was
obtained from both the participants and their guardians. The
data collected in this study were anonymized and required acode to identify specific individuals.

Study Design
This study reports based on the CONSORT (Consolidated
Standards of Reporting Trials) Statement for Randomized Trials
of Nonpharmacologic Treatments [33]. The CONSORTeHEALTH checklist is presented in Multimedia Appendix 1.
A multicenter randomized controlled trial (RCT) was conductedfrom November 2022 to October 2023 in Japan. A researchteam (KM, MN, and SH) at Kagoshima University Hospitaland the University of Fukui designed this RCT. A total of 6
universities and 1 high school were registered as implementation

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Matsumoto et alsites in this study. This clinical trial is registered in the
University Hospital Medical Information Network Center, andan overview of the research protocol is publicly available(UMIN000050064).

Participants and Recruitment
Participants were recruited from 6 universities and 1 high school
in Japan. In total, 89 students gave informed consent, and theeligibility criteria were confirmed. Of them, 77 students met
the eligibility criteria, and they were enrolled in this clinical
trial. The participants were randomly assigned to an intervention
group (ICBT) and a control group (no treatment). Participantsreceived coupons worth JP ¥5000 (equivalent to US $31.30) as
compensation for each of the 2 data submissions. Participants
assigned to the intervention group received compensation atbaseline and at the start of the intervention. Those assigned tothe control group received compensation at baseline and at 10
weeks. High school participants did not receive remuneration,in accordance with their school’s educational policy.

Eligibility and Exclusion CriteriaHigh school or college students between the ages of 15 to 25
years, with a total LSAS score≥30 or higher [27], and with theirown smartphone were eligible. The exclusion criteria werediagnosis of psychiatric disorders such as depression, historyof CBT within 2 years, IQ<85, imminent suicidal risk, and thepresence of advanced diseases such as cancer.

Intervention
Participants assigned to the intervention group were instructedto complete a specific ICBT program entirely through self-help,
using their own smartphones. Participants could contact the
research team if they had any specific questions. It wasrecommended to complete 1 module per week, with automatic
email reminders sent every Monday morning, prompting
participants to engage in the program. If a module was notcompleted by Friday, participants received an automatic email
reminder on Saturday at noon. The first author (KM) developed
an unguided ICBT program for subthreshold SAD in adolescentsand young adults. The ICBT program was built on an e-learning
platform (learningBOX; learningBOX Inc). The ICBT programis based on the Clark and Wells [14] model. The ICBT program
consists of 10 sessions of training on effective CBT components
for social anxiety. Table 1 shows the treatment modules. The
participants in the control group received no treatment; theyalso were asked to refrain from accessing information about
CBT.

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Table 1. The modules and tasks of the treatment course.
ModuleTask

1

Psychoeducation and case-formulation

Developing an idiosyncratic version of the formulation

2

Examine the function of safety behaviors and self-focused Manipulating safety behaviors and self-focused attention with behavioral experiattention
ments

3

Video feedback to correct negative self-image

Updating negative distorted self-images by video feedback in participant’s smartphone

4

Attention training in photographic social situations

Shifting the focus of attention to external information during a conversation orcommunication

5

Behavioral experiments to test negative predictions andassumptions

Observing the reactions of others immediately after behavioral experiments

6

Opinion survey to follow-up behavioral experiments

Updating negative assumptions about failures in social situations

7

Handling anticipatory worry and postevent rumination

Exploring the advantages and disadvantages of worry and rumination

8

Image description

Updating negative self-images and impressions

9

Schema work

Addressing dysfunctional negative beliefs and assumptions

10

Prevent relapse

Summarizing coping strategies for social anxiety and reflecting on the progress ofthe treatment course

Outcomes
Primary Outcome
The primary outcome was the severity of social anxiety, as per
the self-rated LSAS score. The LSAS was developed to measuresocial anxiety [27]. The LSAS contains 24 social situations
related to “fear or anxiety” and “avoidance” that the participants
are asked to rank on a 4-point scale, with 0=never and 4=severe.
The Japanese version of the LSAS has demonstrated reliability
and validity and is widely used in clinical and research settings
in Japan [34]. Response to the ICBT was defined as a decreasein the LSAS by 28% or more [35]. Remission was defined as
an LSAS total score<35, as specified in a previous ICBT studyof SAD conducted in Hong Kong [36]. Conversely, to assess
the risk of exacerbating social anxiety, we defined worsening
as an increase in LSAS of 28% or more.

Secondary Outcomes
The secondary outcomes were the scores on 4 self-administeredscales: the Social Phobia Inventory (SPIN) is a self-rating scalethat measures 3 characteristic aspects of SAD: fear, avoidance,and physiological arousal [37]. In the Japanese version of the
SPIN, 17 questions are answered on a 5-point scale, with 0=not
applicable at all and 4=strongly applicable [38]. The Patient
Health Questionnaire-9 (PHQ-9) was developed to measure
depressive symptoms [39,40]. The first 9 items of the PHQ-9
assess how often various depressive symptoms have occurredin the last 2 weeks. The Generalized Anxiety Disorder-7(GAD-7) scale was developed to measure anxiety levels [40,41].
The first 7 items of the GAD-7 assess how often various anxiety
symptoms have occurred in the last 2 weeks. The EQ-5D-5L
measures the quality of life (QOL) values for calculating
quality-adjusted life years (QALYs) in the economic evaluationof medical technologies [42,43]. In the EQ-5D-5L, the responderanswers questions on 5 dimensions directly related to QOL(mobility, self-care, usual sensitivity, pain or discomfort, andanxiety or depression). Each dimension has 5 levels: noproblems, slight problems, moderate problems, severe problems,
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0=dead and 1.0=in perfect health. We also calculated therecovery rates of the Improved Access to Psychotherapy
program and improvement (recovery) rates considering total
scores in SPIN<19 and PHQ-9<10, simultaneously forcomparison with a UK sample [44].

Sample Size
The sample size was calculated to be 78 using G*Power (version
3.1.9.7; The G*Power Team), which is a free statistical analysis
software [45,46]. The required sample size of this RCT was
estimated to be 52, considering a 2-tailed significance level of.05, a power of 80%, and an estimated effect size of 0.8 [30].
The required sample size above was calculated considering the
50% dropout rate of previous studies with unguided ICBT [47].

Randomization
Randomized allocation was conducted by the minimization
method with a randomization generator [48]. In randomization,
LSAS total score <50 or ≥50, sex (male or female), and facilities
were used as adjustment factors.

Blinding
Blinding was not implemented.

Statistical Analyses
Missing values were imputed using the mice package in R(version 4.3.2; R Foundation for Statistical Computing), a freestatistical software package [49]. Demographic data at baseline
were described, and between-group characteristics wereanalyzed using independent sample 2-tailed t tests. To
investigate significant differences in the change of scores
between groups for both the primary and the secondary outcome
measures, an analysis of covariance (ANCOVA) was conducted.
A covariate factor was the severity of depression determinedby measuring the PHQ-9 total score at baseline. For treatment
response ratio, remission ratio, and recovery ratio, Fisher exact
test was performed, and odds ratios (ORs) with 95% CIs were
calculated. Analyzing the risk of worsening social anxiety
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measured in LSAS involved the calculation of risk ratio, relativerisk reduction (RRR), absolute risk reduction (ARR), andnumber needed to treat (NNT). Statistical analyses were
implemented by using R (version 4.3.2). A significance levelof .05 was used for all analyses.

Results
Recruitment
Among the 38 participants assigned to the intervention group,4 declined research participation after the preintervention

Matsumoto et alassessment. A total of 31 participants completed the ICBT
program at least once, while 3 did not access the intervention
program at all. Therefore, the dropout rate from this ICBT
program was 9% (3/34), the implementation rate of ICBT was
91% (31/34), and the completion rate was 65% (22/34). Of the
39 participants assigned to the control group, 1 declined research
participation, and data on outcomes could not be obtained for
2 students due to unavailability. Following the predetermined
analysis plan, the statistical analysis included data from 31
participants in the intervention group and 38 in the control
group. Figure 1 shows the participant flow diagram.

Figure 1. CONSORT (Consolidated Standards of Reporting Trials) flow diagram.

Demographical and Characteristic Data
Table 2 shows the demographics, clinical characteristics, andbaseline outcomes of the participants included in the analyses.
The level of depression, measured by the PHQ-9, in the control

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group, was significantly higher than the intervention group atbaseline; however, clinically, both groups fell within the rangeof “mild depressive symptoms” (total score 5-9) [50]. No
significant differences were observed in other outcomes.

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Table 2. Demographical and characteristic data, and the total scores of outcomes at baseline.
Demographical and characteristic data

ICBTa group (n=31)

Control group (n=38)

P value (unpaired t test)

Sex (female), n (%)

20 (65)25 (66)

N/Ab

Age, mean (SD)21.61 (2.06)

21.39 (2.32).68

LSAS , mean (SD)58.38 (19.17)

59.08 (20.77).88

SPINd, mean (SD)25.39 (10.27)

27.42 (12.50).47

PHQ-9e, mean (SD)4.87 (4.38)

6.16 (4.29).05

GAD-7f, mean (SD)

4.13 (4.52)

4.21 (3.30).31

EQ-5D-5L, mean (SD)

0.9160 (0.079)

0.889 (0.114)

.28

c

a

ICBT: internet-based cognitive behavioral therapy.

b

N/A: not applicable.

c

LSAS: Liebowitz Social Anxiety Scale.

d

SPIN: Social Phobia Inventory.

e

PHQ-9: Patient Health Questionnaire -9.

f

GAD-7: Generalized Anxiety Disorder-7.

Outcomes and Estimation
Primary Outcome
The reduction in LSAS total score from baseline topostintervention assessment was significantly greater in theintervention group compared to the control group by 11.62 (95%

CI 1.67-21.56; F1,66=3.91; P=.02). Figure 2 presents the change
in LSAS total score from baseline to postintervention
assessment. The change in LSAS total score frompreintervention to postintervention assessment in theintervention group was significantly larger than that in thecontrol group by 9.39 (95% CI 1.31-17.48; F1,66=4.65; P=.01).

Figure 2. Liebowitz Social Anxiety Scale total score. The graphic presents mean and 95% CI. ICBT: internet-based cognitive behavioral therapy.

Secondary Outcome
Table 3 shows the analyses for primary and secondary outcomesin ANCOVA.

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Table 3. Difference of score in outcomes, P value, and effect size.
ICBTa group, meanchange (SD)Control, mean F test (df=2, 66; ANCO- P value (ANCO- Effect sizechange (SD)
VA)
(Hedge g)
VAb)

Baseline to postintervention assessment

16.90 (22.63)

4.16 (17.38)

3.91

.02

0.64

Preintervention to postintervention assessment

14.90 (14.86)

N/Ad

4.65

.01

0.66

Baseline to postintervention assessment

10.87 (11.40)

2.87 (8.69)

5.39

.007

0.80

Preintervention to postintervention assessment

11.19 (9.33)

N/A

7.23

.01

0.93

Baseline to postintervention assessment

0.68 (3.36)–0.32 (2.85)

1.19

.31

0.22

Preintervention to postintervention assessment

1.42 (2.98)

N/A

2.96

.06

0.49

Baseline to postintervention assessment

0.29 (2.98)–1.03 (3.17)

1.61

.21

0.09

Preintervention to postintervention assessment

0.97 (2.83)

N/A

4.15

.02

0.32

Baseline to postintervention assessment–0.0299 (0.09)

0.0079 (0.09)

1.61

.21

0.003

Preintervention to postintervention assessment–0.0301 (0.11)

N/A

1.41

.25

0.0004

Outcome and evaluation point

LSASc

SPINe

PHQ-9fGAD-7g

EQ-5D-5La

ICBT: internet-based cognitive behavioral therapy.

b

ANCOVA: analysis of covariance.

c

LSAS: Liebowitz Social Anxiety Scale.

d

N/A: not applicable.

e

SPIN: Social Phobia Inventory.

f

PHQ-9: Patient Health Questionnaire-9.

g

GAD-7: Generalized Anxiety Disorder-7.

The reduction in SPIN total score from baseline topostintervention assessment was significantly greater in theintervention group compared to the control group by 8.05 (95%
CI 3.02-13.08; F1,66=5.39; P=.007). The change in SPIN total
score from preintervention to postintervention assessment in
the intervention group was significantly larger than that in thecontrol group by 8.26 (95% CI 3.75-12.78; F1,66=7.23; P=.01).
The reduction in PHQ-9 total score from baseline topostintervention assessment was greater in the intervention
group compared to the control group by 1.15 (95% CI 0.41-2.70;
F1,66=1.19; P=.31), not significantly. The change in PHQ-9 total
score from preintervention to postintervention assessment in
the intervention group was larger than that in the control groupby 1.75 (95% CI 0.28-3.23; F1,66=2.96; P=.06), not significantly.
The reduction in GAD-7 total score from baseline topostintervention assessment was greater in the intervention
group compared to the control group by 1.24 (95% CI –3.05 to
2.79; F1,66=1.66; P=.21), not significantly. The change in GAD-7
total score from preintervention to postintervention assessment
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the control group by 1.81 (95% CI 0.31-3.33; F1,66=4.15; P=.02).
The reduction in QALY measured by EQ-5D-5L from baseline
to postintervention assessment was greater in the intervention
group compared to the control group by –0.0388 (95% CI –0.09
to 0.008; F1,66=1.41; P=.25), not significantly. The change in
QALY measured by EQ-5D-5L from preintervention to
postintervention assessment in the intervention group was larger
than that in the control group by 0.0366 (95% CI –0.0120 to
0.0852; F1,66=1.31; P=.28), not significantly.

Ancillary Analyses
Table 4 presents Fisher exact test results for treatment response
rate, remission rate, recovery rate, and risk ratio. The treatment
response rate in the intervention group was significantly higher
at 61% (19/31) compared to the control group at 24% (9/38;
P=.003; OR 4.97, 95% CI 1.61-16.53). The recovery rate in theintervention group was substantially higher at 68% (21/31)
compared to the control group at 34% (13/38; P=.008; OR 3.95,
95% CI 1.32-12.56). Regarding the risk of deterioration, the
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Matsumoto et alintervention group had a higher but nonsignificant rate of 6%(2/31) compared to the control group 24% (9/38; P=.10).

Table 4. Results of Fisher exact testa.
Result

ICBTb group (n=31), n (%)

Control group (n=38), n (%)

ORc (95% CI)

P value

Response

19 (61)9 (24)

4.97 (1.61-16.53).003

Remission

12 (39)9 (24)

2.01 (0.64-6.60).20

Recovery21 (68)13 (34)3.95 (1.32-12.56)

.008

Worse

2 (6)

9 (24)

0.23 (0.02-1.23).10aDefinition of clinically significant change: response: a decrease in the Liebowitz Social Anxiety Scale (LSAS) by 28% or more; remission: an LSAS
total score<35; recovery: total scores in Social Phobia Inventory<19 and Patient Health Questionnaire-9<10; and worse: an increase in LSAS of 28%
or more.
b

ICBT: internet-based cognitive behavioral therapy.

c

OR: odds ratio.

Adverse Events and Harms
No severe adverse events were reported for this study period.
Table 5 presents the relative risk, RRR, ARR, and NNT. The
results of the RRR imply that ICBT reduces the occurrence ofdeterioration events by 73% compared to no treatment in thecontrol group. The results of the ARR imply that ICBT can save
17% more adolescents and young adults from deterioration
events of social anxiety compared to no treatment. The resultsof the NNT suggest that unguided ICBT could be required for
5.8 individuals with subthreshold SAD in adolescents and young
adults to prevent deterioration in symptoms for 1 individual.

Table 5. Results of worse risk analysesa.
Result

ICBTb group (worse=6%) and control group (worse=24%) (%)

RRc

26

RRRd

73

ARRe

17

NNTf

6

a

Formula: RR=percentage of worse event ICBT group/control group; RRR=1–RR; ARR=percentage of worse event in control group–ICBT group; and
NNT=1/ARR.
b

ICBT: internet-based cognitive behavioral therapy.

c

RR: relative risk.

d

RRR: relative risk reduction.

e

ARR: absolute risk reduction.

f

NNT: number needed to treat.

Discussion
Principal Findings
This study evaluated the effectiveness of unguided ICBT foradolescents and young adults with subthreshold SAD througha multicenter RCT. The dropout rate in the intervention group
was 9% (3/34), with an ICBT implementation rate of 91%(31/34) and a completion rate of 65% (22/34). The participants
who conducted ICBT showed a significant reduction in social
anxiety symptoms compared to those who did not receive
treatment. Key indicators representing substantial symptom
improvement, namely, treatment response rate (ICBT: 19/31,
61% vs control: 9/38, 24%; P=.003) and recovery rate (ICBT:
21/31, 68% vs control: 13/38, 34%; P=.008), demonstrated
significant differences between the groups, with the intervention
group showing better outcomes. No serious adverse events wereobserved in either group. Regarding deterioration events in
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RenderXsocial anxiety symptoms, there were 2 (6%) out of 31 cases in
the intervention group and 9 (24%) out of 38 cases in the control
group, but the difference was not statistically significant (P=.10).
In summary, this study indicates that ICBT is an effective
intervention approach for improving social anxiety symptoms
in adolescents and young adults with subthreshold SAD.

Comparison With Prior WorkA systematic review and meta-analysis of outcomes from 20
RCTs on SAD meeting clinical diagnostic criteria demonstrated
that ICBT is effective in improving social anxiety symptoms,
with a moderate effect size (Hedge g=0.55) [51]. In this study,
unguided ICBT was shown to be sufficiently effective forsubthreshold SAD in adolescents and young adults. This expands
the evidence on CBT studies for SAD from several perspectives.
The first perspective is the absence of therapist guidance. Many
conventional ICBT studies for SAD have included therapist
guidance [26,30]. Our results suggest that providing unguided
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JMIR PEDIATRICS AND PARENTINGICBT to students with subthreshold SAD significantly reduces
social anxiety symptoms measured by LSAS compared to theuntreated group with a moderate effect size (Hedge
g=0.66-0.66). The moderate effect size calculated in this RCT
was comparable to a meta-analysis of 10 RCTs on face-to-face
CBT for SAD [15]. Most of the participants assigned to theintervention group in this RCT achieved the treatment courseof the Clark and Wells [14] model. Therefore, it appears that,even without guidance, significant improvements in social
anxiety symptoms can be achieved with sufficient engagement.
Another perspective is related to the acceptance of ICBT foradolescents and young adults who do not meet the diagnostic
criteria of SAD but are at high risk. As an application in clinicalpsychiatric care, a longitudinal cohort study has reported thatICBT enhances treatment adherence and reduces social anxiety
symptoms in adults at risk for the onset of SAD [52]. Since
SAD tends to manifest in adolescence [6], similar effects forsubthreshold SAD may be observed in student support services
in high schools and universities. Given the high likelihood ofanxiety disorders persisting into adolescence [53], preventing
the onset of mental disorders through early intervention in
high-risk individuals is an important endeavor. Therefore, future
research on subthreshold SAD in adolescents should consider
conducting longitudinal cohort studies within the context of
ICBT studies. Additionally, 23.3% of adolescents and young
adults experience some form of anxiety, and among them, 39.1%
use some form of health care service [54]. Only 108 (39.1%)of the 277 individuals sought medical help for their mental
health issues, while the remaining 169 (60.9%) did not accesshealthcare. Since young individuals with social anxiety tend to
avoid seeking help and contacting others [55], unguided ICBT
may have the potential to meet their needs.
A previous preliminary study involving 17 adolescents with
SAD who underwent ICBT reported high satisfaction with
unguided ICBT through web-based questionnaires andsemistructured interviews [56]. Participants who received guided
ICBT in this preliminary investigation particularly appreciatedthe ability to access the ICBT program multiple times, allowing
for repeated self-help. In this RCT, among the 34 participantsin the intervention group, the majority (n=31, 91%) performed
an ICBT module at least once. While 65% (n=31) completed
the full ICBT course, those who completed the entire treatment
course—up to module 9, corresponding to the Clark and Wells

Matsumoto et al[14] model—accounted for 82% (n=28). According to theseresults, unguided ICBT is probably more acceptable foradolescents and young adults with subthreshold SAD.
Preliminary findings from our results also indicate that receiving
complete self-help ICBT reduced the worsening of SAD by
73%. In addition to its short-term efficacy, unguided self-help
ICBT may potentially prevent deterioration—that is, inhibiting
the onset of SAD—in youths with subthreshold SAD. Even in
the absence of guidance from CBT therapists, implementing
ICBT based on the Clark and Wells [14] model may bebeneficial for young adults and adolescents with SAD
symptoms.

Limitations
This study has several limitations that may increase the risk ofbias. First, the primary outcome, the self-reported LSAS, was
not blinded. The participants assigned to the intervention group
may have positive expectations regarding the intervention, which
could potentially affect the outcome. In the future, RCTs withblinded assessors should be conducted. Second, the control
condition in this study was a no-treatment condition. To control
for biases introduced by receiving the intervention or notreatment, future RCTs should consider using sham applications
as psychological placebos to ensure blinding. Third, the evidence
obtained in this RCT pertains to short-term effectiveness andcannot speak to the medium- to long-term effects. Particularly,
to assess the effects on preventing the deterioration of social
anxiety symptoms and preventing the onset of SAD, futureintervention studies for subthreshold SAD should include a
randomized cohort study with an observation period of several
years.

Conclusions
This multicenter RCT, conducted in Japan, has demonstrated
that unguided ICBT can reduce social anxiety symptoms inadolescents and young adults with subthreshold SAD. Unguided
ICBT appears to be a user-friendly intervention approach forsupporting subthreshold SAD. Complete self-help ICBT may
be a practical treatment approach that prevents deterioration inadolescents and young adults at high risk of developing SAD.
Future research should incorporate study designs measuringlong-term outcomes and focus on conducting cohort studies
aimed at assessing the risk of clinically diagnosed SAD.

Acknowledgments
This study was supported by the Platform for All Regions Kyushu and Okinawa for Startup-ecosystem 2022 of the Japan Scienceand Technology Agency. The 2023 Kagoshima University Young Researcher Support Grant (representative: KM) was supported
for English proofreading and some manuscript subscriptions.

Conflicts of Interest
None declared.

Multimedia Appendix 1
CONSORT-eHEALTH (V 1.6.1).
[PDF File (Adobe PDF File), 290 KB-Multimedia Appendix 1]

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Abbreviations
ANCOVA: analysis of covariance
ARR: absolute risk reduction
CBT: cognitive behavioral therapy
CONSORT: Consolidated Standards of Reporting Trials
GAD-7: Generalized Anxiety Disorder-7
ICBT: internet-based cognitive behavioral therapy
LSAS: Leibovitz Social Anxiety Scale
NNT: number needed to treat
OR: odds ratio
PHQ-9: Patient Health Questionnaire-9
QALY: quality-adjusted life years
QoL: quality of life
RCT: randomized controlled trial
RRR: relative risk reduction
SAD: social anxiety disorder
SPIN: Social Phobia Inventory

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Edited by G Eysenbach, S Badawy; submitted 24.12.23; peer-reviewed by Ka-Po Wong; comments to author 21.03.24; revised version
received 25.03.24; accepted 22.04.24; published 22.07.24
Please cite as:
Matsumoto K, Hamatani S, Shiga K, Iiboshi K, Kasai M, Kimura Y, Yokota S, Watanabe K, Kubo Y, Nakamura M
Effectiveness of Unguided Internet-Based Cognitive Behavioral Therapy for Subthreshold Social Anxiety Disorder in Adolescents andYoung Adults: Multicenter Randomized Controlled Trial
JMIR Pediatr Parent 2024;7:e55786
URL: https://pediatrics.jmir.org/2024/1/e55786
doi: 10.2196/55786
PMID: 39037759©Kazuki Matsumoto, Sayo Hamatani, Kiko Shiga, Kiyoko Iiboshi, Makiko Kasai, Yasuhiro Kimura, Satoshi Yokota, Katsunori
Watanabe, Yoko Kubo, Masayuki Nakamura. Originally published in JMIR Pediatrics and Parenting (https://pediatrics.jmir.org),
22.07.2024. This is an open-access article distributed under the terms of the Creative Commons Attribution License(https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,provided the original work, first published in JMIR Pediatrics and Parenting, is properly cited. The complete bibliographic
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